Wind Power Wind Power
Fundamentals Fundamentals
Presented by:
Alex Kalmikov and Katherine Dykes With contributions from:
Kathy Araujo
PhD Candidates, MIT Mechanical
Engineering, Engineering Systems and U b Pl i
Urban Planning
MIT Wind Energy Group &
Renewable Energy Projects in Action Renewable Energy Projects in Action Email: wind@mit.edu
Overview
History of Wind Power History of Wind Power
Wind Physics Basics
Wind Power Fundamentals
Technology Overview Technology Overview
Beyond the Science and Technology
What’s underway @ MIT
Wind Power in History …
Brief History – Early Systems Harvesting wind power isn’t exactly a new idea – sailing ships, wind-mills, wind-pumps
1st Wind Energy Systems
– Ancient Civilization in the Near East / Persia
– Vertical-Axis Wind-Mill: sails connected to a vertical shaft connected to a grinding stone for milling
Wind in the Middle Ages
P t Mill I t d d i N th E
– Post Mill Introduced in Northern Europe
– Horizontal-Axis Wind-Mill: sails connected to a
horizontal shaft on a tower encasing gears and axles for translating horizontal into rotational motion
for translating horizontal into rotational motion Wind in 19th century US
– Wind-rose horizontal-axis water-pumping wind-mills g found throughout rural America
Torrey, Volta (1976) Wind-Catchers: American Windmills of Yesterday and Tomorrow. Stephen Green Press, Vermont.
Righter, Robert (1996) Wind Energy in America. University of Oklahoma Press, Oklahoma.
Brief History - Rise of Wind Powered Electricity
1888: Charles Brush builds first large-size wind electricity generation turbine (17 m diameter y g ( wind rose configuration, 12 kW generator) 1890s: Lewis Electric Company of New York
sells generators to retro-fit onto existing wind mills
1920s 1950s: P ll t 2 & 3 bl d 1920s-1950s: Propeller-type 2 & 3-blade
horizontal-axis wind electricity conversion systems (WECS)
1940s – 1960s: Rural Electrification in US and Europe leads to decline in WECS use
Torrey, Volta (1976) Wind-Catchers: American Windmills of Yesterday and Tomorrow. Stephen Green Press, Vermont.
Righter, Robert (1996) Wind Energy in America. University of Oklahoma Press, Oklahoma.
Brief History – Modern Era
Key attributes of this period:
• Scale increase
• Commercialization
• Competitiveness
• Grid integration
Catalyst for progress: OPEC Crisis (1970s)
• Economics
• Energy independence
• Environmental benefits
Turbine Standardization:
Turbine Standardization:
3-blade Upwind Horizontal-Axis
on a monopole tower
Source for Graphic: Steve Connors, MIT Energy Initiative
on a monopole tower
Wind Physics Basics …
Origin of Wind
Wind – Atmospheric air in motion
Energy source
Solar radiation differentially
b b d b th f
absorbed by earth surface converted through convective processes due to temperature differences to air motion
Spatial Scales
differences to air motion p
Planetary scale: global circulation Synoptic scale: weather systems
M l l l t hi
Meso scale: local topographic or thermally induced circulations
Micro scale: urban topography Source for Graphic: NASA / GSFC
Wind types
• Planetary circulations:
– Jet stream – Trade winds
Polar jets – Polar jets
• Geostrophic winds
• Thermal winds
• Gradient winds
• Katabatic / Anabatic winds – topographic winds
• Bora / Foehn / Chinook – downslope wind storms
• Sea Breeze / Land Breeze
• Convective storms / Downdrafts
• Hurricanes/ Typhoons
• Tornadoes
• Gusts / Dust devils / Microbursts
• Gusts / Dust devils / Microbursts
• Nocturnal Jets
• Atmospheric Waves
Wind Resource Availability and Variability
Source: Steve Connors, MIT Energy Initiative
Source for Wind Map Graphics: AWS Truewind and 3Tier
Fundamentals of Wind Power … Wind Power Fundamentals Wind Power Fundamentals …
Fundamental Equation of Wind Power
Wi d P d d
– Wind Power depends on:
• amount of air (volume)
• speed of air (velocity)
• mass of air (density)
A
flowing through the area of interest (flux) Kinetic Energy definition:
A v
– Kinetic Energy definition:
• KE = ½ * m * v 2
– Power is KE per unit time: dm
m& = d mass flux
Power is KE per unit time:
• P = ½ * * v 2
– Fluid mechanics gives mass flow rate
&
dtm
(density * volume flux):
• dm/dt = ρ* A * v Thus:
– Thus:
• P = ½ * ρ * A * v 3
•
Power ~ cube of velocity• Power ~ air density
• Power ~ rotor swept area A= πr2
Efficiency in Extracting Wind Power
Betz Limit & Power Coefficient:
• Power Coefficient, Cp, is the ratio of power extracted by the turbine to the total contained in the wind resource Cp = P /P
to the total contained in the wind resource Cp = PT/PW
• Turbine power output
PTT = ½ * ρ * A * v 3 * Cp
• The Betz Limit is the maximal possible Cp = 16/27
• 59% efficiency is the BEST a conventional wind turbine can do in
• 59% efficiency is the BEST a conventional wind turbine can do in extracting power from the wind
Power Curve of Wind Turbine
Capacity Factor (CF):
• The fraction of the year the turbine generator is operating at rated (peak) power
rated (peak) power
Capacity Factor = Average Output / Peak Output ≈ 30%
• CF is based on both the characteristics of the turbine and the site characteristics (typically 0.3 or above for a good site)
Wind Frequency Distribution Power Curve of 1500 kW Turbine
0.06 0.08 0.1 0.12
0 0.02 0.04
<1 -2 -3 -4 -5 -6 -7 -8 -9 0 1 2 3 4 5 6 7 8 9 20
Nameplate Capacity
< 1- 2- 3- 4- 5- 6- 7- 8- 9-1 10-1 11-1 12-1 13-1 14-1 15-1 16-1 17-1 18-1 19-2
wind speed (m/s)
Lift and Drag Forces
Wind Power Technology …
Wind Turbine
Al t ll l t i l E th i d d ith t bi f t
• Almost all electrical power on Earth is produced with a turbine of some type
• Turbine – converting rectilinear flow motion to shaft rotation through rotating airfoils
Type of Combustion Primay Electrical
G ti T P C i
Turbine Type
Generation Type Gas Steam Water Aero Power Conversion
³ Traditional Boiler External • Shaft Generator
³ Fluidized Bed External • Shaft Generator
Combustion – –
Integrated Gasification Both • • Shaft Generator
Integrated Gasification Both • • Shaft Generator
Combined-Cycle – –
Combustion Turbine Internal • Shaft Generator
Combined Cycle Both • • Shaft Generator
³ Nuclear • Shaft Generator
Diesel Genset Internal Shaft Generator
Micro-Turbines Internal • Shaft Generator
Fuel Cells Direct Inverter
Hydropower • Shaft Generator
³ Biomass & WTE External • Shaft Generator
Windpower • Shaft Generator
Photovoltaics Direct Inverter
³ Solar Thermal • Shaft Generator
³ Geothermal • Shaft Generator
³ Geothermal • Shaft Generator
Wave Power • Shaft Generator
Tidal Power • Shaft Generator
³ Ocean Thermal • Shaft Generator
Source: Steve Connors, MIT Energy Initiative
Wind Turbine Types
Horizontal-Axis – HAWT
• Single to many blades - 2, 3 most efficient
• Upwind downwind facing
• Upwind, downwind facing
• Solidity / Aspect Ratio – speed and torque
• Shrouded / Ducted – Diffuser Augmented Wind Turbine (DAWT)
Wind Turbine (DAWT) Vertical-Axis – VAWT
• Darrieus / Egg-Beater (lift force driven)
• Savonius (drag force driven)
Photos courtesy of Steve Connors, MITEI
Wind Turbine Subsystems
– Foundation – Tower
– Nacelle
– Hub & Rotor – DrivetrainDrivetrain
– Gearbox – Generator
– Electronics & ControlsElectronics & Controls – Yaw
– Pitch – Braking – Braking
– Power Electronics – Cooling
Diagnostics – Diagnostics
Source for Graphics: AWEA Wind Energy Basics, http://www.awea.org/faq/wwt_basics.html
Foundations and Tower
• Evolution from truss (early 1970s) to monopole towers
• Many different configurations proposed for offshore
• Many different configurations proposed for offshore
Images from National Renewable Energy Laboratory
Nacelle, Rotor & Hub
• Main Rotor Design Method (ideal case):
1 Determine basic configuration:
1. Determine basic configuration:
orientation and blade number
2. take site wind speed and desired power output
power output
3. Calculate rotor diameter (accounting for efficiency losses)
4 Select tip speed ratio (higher Æ 4. Select tip-speed ratio (higher Æ
more complex airfoils, noise) and blade number (higher efficiency with more blades)
more blades)
5. Design blade including angle of attack, lift and drag characteristics 6 Combine with theory or empirical 6. Combine with theory or empirical
methods to determine optimum blade shape
Graphic source Wind power: http://www.fao.org/docrep/010/ah810e/AH810E10.htm
Wind Turbine Blades
• Blade tip speed:
• 2-Blade Systems and Teetered Hubs:
Teetered Hubs:
• Pitch Pitch control:
http://guidedtour.windpower.org/en/tour/wres/index.htm
Electrical Generator
• Generator:
– Rotating magnetic field induces current
• Synchronous / Permanent Magnet Generator
– Potential use without gearbox
Hi t i ll hi h t ( f th t l )
– Historically higher cost (use of rare-earth metals)
• Asynchronous / Induction Generator
– Slip (operation above/below synchronous speed) possible
Masters, Gilbert, Renewable and Efficient Electric Power Systems, Wiley-IEEE Press, 2003 http://guidedtour.windpower.org/en/tour/wtrb/genpoles.htm.
p ( p y p ) p
– Reduces gearbox wear
Control Systems & Electronics
• Control methods
– Drivetrain Speed
• Fixed (direct grid connection) and Variable (power electronics for indirect grid connection)
indirect grid connection)
– Blade Regulation
• Stall – blade position fixed, angle
f tt k i ith i d
of attack increases with wind speed until stall occurs behind blade
• Pitch – blade position changes with wind speed to actively
control low speed shaft for a
control low-speed shaft for a
more clean power curve
Wind Grid Integration
• Short-term fluctuations and forecast error
• Potential solutions undergoing research:
G id I t ti T i i I f t t
– Grid Integration: Transmission Infrastructure, Demand-Side Management and Advanced Controls
S f
– Storage: flywheels, compressed air, batteries, pumped-hydro, hydrogen, vehicle-2-grid (V2G)
9000 10000 11000 12000
MW
4000 5000 6000 7000 8000 9000
Wind Production in Wind Forecast
Real Wind Production Wind Market Program
Left graphic courtesy of ERCOT
Right graphic courtesy of RED Electrica de Espana
3000 10:00
11:00 12:00
13:00 14:00
15:00 16:00
17:00 18:00
19:00 20:00
21:00 22:00
23:00 0:00 1:00
2:00 3:00
4:00 5:00
6:00 7:00
8:00
9:00 Time 23-24/01/2009
Future Technology Development
• Improving Performance:
– Capacity: higher heights, larger blades, superconducting magnets
magnets
– Capacity Factor: higher heights, advanced control methods (individual pitch, smart-blades), site-specific designs
• Reducing Costs:
– Weight reduction: 2-blade designs, advanced materials, direct drive systemsy
– Offshore wind: foundations, construction and maintenance
Future Technology Development
• Improving Reliability and Availability:
– Forecasting tools (technology and models) – Dealing with system loadsDealing with system loads
• Advanced control methods, materials, preemptive diagnostics and maintenance
– Direct drive – complete removal of gearbox
• Novel designs:
– Shrouded floating direct drive and high-altitude concepts – Shrouded, floating, direct drive, and high-altitude concepts
Sky Windpower
Going Beyond the Science & g y Technology of Wind…
Source: EWEA, 2009
Wind Energy Costs Wind Energy Costs
Source: EWEA, 2009
% Cost Share of 5 MW Turbine Components
Source: EWEA, 2009, citing Wind Direction, Jan/Feb, 2007
Costs -- Levelized Comparison Costs Levelized Comparison
Reported in US DOE. 2008 Renewable Energy Data Book
Policy Support Historically
US federal policy for wind energy
– Periodic expiration of Production Tax Credit (PTC) in 1999, p ( ) , 2001, and 2003
– 2009 Stimulus package is supportive of wind power – Energy and/or Climate Legislation?Energy and/or Climate Legislation?
Annual Change in Wind Generation Capacity for US
W] 2400
900 1400 1900
ation Capacity [MW
PTC Expirations
-100 400 900
981 983 985 987 989 991 993 995 997 999 001 003 005
Delta-Genera 1 1 1 1 1 1 1 1 1 1 2 2 2
US Denmark
1Wiser, R and Bolinger, M. (2008). Annual Report on US Wind Power: Installation, Cost, and Performance Trends.
US Department of Energy – Energy Efficiency and Renewable Energy [USDOE – EERE].
Policy Options Available
Feed-in Tariff
G t d M k t (P bli l d)
Policy Options Available
Guaranteed Markets (Public land)
National Grid Development
Carbon Tax/Cap and Trade Others:
Quota/Renewable Portfolio Standard
Renewable Energy Credits (RECs)/
Green Certificates Green Certificates
Production Tax Credit (PTC)
Investment Tax Credit (ITC) Investment Tax Credit (ITC)
Communities
Question: At the urban level, do we apply the same level of scrutiny
to flag and light poles, public art, signs and other power plants as we do i d t bi ?
wind turbines?
Considerations: Jobs and industry development; sound and flicker;
Ch i i ( h i l & t l) I t t d l i
Changing views (physical & conceptual); Integrated planning;
Cambridge, MA
Graphics Source: Museum of Science Wind Energy Lab, 2010
The Environment
• Cleaner air -- reduced GHGs, particulates/pollutants, waste; minimized opportunity for oil spills, natural gas/nuclear plant leakage; more sustainable effects
• Planning related to wildlife migration and habitats
• Life cycle impacts of wind power relative to other energy sources
• Some of the most extensive monitoring has been done in Denmark
– finding post-installation benefits
• Groups like Mass Audubon,
Natural Resources Defense Council, World Wildlife Fund support wind power projects like Cape Wind
Graphic Source: Elsam Engineering and Enegi and Danish Energy Agency
What’s underway at MIT
What’s underway at MIT…
Turbine Photo Source: http://www.skystreamenergy.com/skystream-info/productphotos.php
MIT Project Full Breeze
• 3 and 6+ months of data at
• 3 and 6+ months of data at two sites on MIT’s Briggs Field
• Complemented with statistical analysis using Measure-
Met station 2
analysis using Measure- Correlate-Predict method
Analysis Method MCP CFD MCP CFD MCP CFD
Height [m] 20 20 26 26 34 34
Mean Wind Speed [m/s] 3.4 2.9 n/a 3.0 4.0 3.2
Power Density [W/m^2] 46.5 51.7 n/a 60.4 74.6 70.9
Annual Energy Output
[kW-hr] 1,017 1,185 n/a 1,384 1,791 1,609
[kW hr]
Annual Production CFD
[kW-hr] n/a 1,136 n/a 1,328 n/a 1,558
Capacity Factor 5% 6% n/a 7% 9% 8%
Operational Time 38% 28% n/a 30% 51% 33%
Met station 1
• Research project using Computational Fluid Dynamics techniques
Analysis Method MCP CFD MCP CFD MCP CFD
Height [m] 20 20 26 26 34 34
Mean Wind Speed
[m/s] 3.3 2.7 3.7 2.9 n/a 3.1
Power Density [W/m^2] 39.4 41.9 55.6 50.2 n/a 60.5
Annual Energy Output
for urban wind applications
• Published paper at
Annual Energy Output
[kW-hr] 817 974 1,259 1,193 n/a 1,430
Annual Production
CFD [kW-hr] n/a 931 n/a 1,135 n/a 1,377
Capacity Factor 4% 5% 6% 6% n/a 7%
Operational Time 35% 26% 45% 29% n/a 32%
AWEA WindPower 2010 conference in Texas
Spatial Analysis of Wind Resource at MIT
3D model of MIT campus
3D simulations of wind resource structure at MIT
Wind speed Turbulence intensity
(a) (c)
(b) (d)
Wind Power Density at MIT
Wind Power Density
(W/m2)
Wind Power Density (W/m2)
